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United States Patent | 5,331,221 |
Ganesan ,   et al. | July 19, 1994 |
Gain linearity problems caused by impact ionization in a active MOS device are avoided by connecting an MOS shield device in series with the active MOS device so that the overall supply voltage is split across two devices, keeping both devices in a region of operation well below where impact ionization becomes a significant problem. The gate of the MOS shield device is maintained at a voltage proportional to its drain voltage, thereby keeping the device in the saturation mode and avoiding an abrupt mode change associated with prior art shield circuits.
Inventors: | Ganesan; Apparajan (Salem, NH); Ferguson, Jr.; Paul F. (Tewksbury, MA); Robertson; David H. (Somerville, MA) |
Assignee: | Analog Devices, Inc. (Norwood, MA) |
Appl. No.: | 110327 |
Filed: | August 23, 1993 |
Current U.S. Class: | 327/362; 327/328; 327/427; 327/544 |
Intern'l Class: | H03K 017/14; H03K 003/013; H03F 001/30 |
Field of Search: | 307/308,304,491,493,494,568,296.1,296.4,296.5,296.8,443,307 |
4717846 | Jan., 1988 | Ando | 307/443. |
4740713 | Apr., 1988 | Sakurai et al. | 307/443. |
4920287 | Apr., 1990 | Hartgring et el. | 307/443. |
4996446 | Feb., 1991 | Nakada | 307/443. |
Foreign Patent Documents | |||
0210155 | Jan., 1987 | EP. |
Design Considerations for a High-Performance Three Micrometer CMOS Analog Standard-Cell Library, C. A. Laber et al. U. Gatti et al.: "A Novel CMOS Linear Transconductance Cell for Continuous-Time Filters". |